Os8N3 is a host disease-susceptibility gene for bacterial blight of rice

Many bacterial diseases of plants depend on the interaction of type III effector genes of the pathogen and disease-susceptibility genes of the host. The host susceptibility genes are largely unknown. Here, we show that expression of the rice gene Os8N3, a member of the MtN3 gene family from plants and animals, is elevated upon infection by Xanthomonas oryzae pv. oryzae strain PX099(A) and depends on the type III effector gene pthXo1. Os8N3 resides near xa13, and PX099(A) failed to induce Os8N3 in rice lines with xa13. Silencing of Os8N3 by inhibitory RNA produced plants that were resistant to infection by strain PX099(A) yet remained susceptible to other strains of the pathogen. The effector gene avrXa7 from strain PXO86 enabled PX099(A) compatibility on either xa13- or Os8N3-silenced plants. The findings indicate that Os8N3 is a host susceptibility gene for bacterial blight targeted by the type III effector PthXo1. The results support the hypothesis that X. oryzae pv. oryzae commandeers the regulation of otherwise developmentally regulated host genes to induce a state of disease susceptibility. Furthermore, the results support a model in which the pathogen induces disease susceptibility in a gene-for-gene manner.